While waiting at a slippery patch in Icemule, I saw that a snow crone had a ruby-pommeled mithril rapier. I killed it and when I looted it I got the regular "You discard its useless equipment" message instead of it telling me it had an unusual weapon. I thought I'd pass this on since this is usually the only way I realize something I killed had a feeder weapon. I've also bugged it in game.

There were two in the room - I killed both of them and didn't get the message for either but the weapon was on the ground. I've since found a few more weapons but haven't had the problem again.